• Journal of Korean Society of Environmental Engineers
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• v.38 no.7
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• pp.343-352
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• 2016

Effects of grinding time and chemicals dosage in arsenic removal from contaminated paddy soil in China were investigated using lab scale attrition and froth flotation combining process. Arsenic concentration in the field soil was 76.51 mg/kg, exceeding Korean and Chinese standards, and predominant arsenic compounds fraction in sequential extraction was "residual" (over 80%). After wet sieving, soil with >2 mm and < 0.038 mm showed concentration lower than 'Warning Level' in Korea. Soil with 0.038-0.075 mm, showing the highest concentration, was discarded since it occupied minor weight fraction (10.1%). Thus soil between 0.075 and 2 mm was only used in the combining process. The highest Arsenic concentration in progeny fragments smaller than 0.038 mm reached up to 981.66 mg/kg after 5 min of attrition. Optimal dosage of collector ($C_5H_{11}OCS_2K$) and modifier ($Na_2S$ and $CuSO_4$) in froth flotation process for the selective separation of the chipped progeny particles from the parent fragments were determined both as 200 g/ton. Arsenic removal efficiency in froth flotation process was 38.47% and it was increased to 72.74% in additional flotation process, scavenging. Average arsenic concentration after overall process - wet sieving, attrition and froth flotation - was estimated to 16.45 mg/kg.

• Korean journal of food and cookery science
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• v.28 no.3
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• pp.275-283
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• 2012

This study was conducted to monitor the quality characteristics of Lespedeza cuneata ethanolic extracts, by a response surface methodology. The independent variables were the extraction temperature ($35{\sim}95^{\circ}C}$), extraction time (2~10 hr), and ethanol concentration (10~90%). The coefficients of the determinations (R2) were 0.8562 (p<0.1), 0.9787 (p<0.01), and 0.8344 (p<0.1) in total polyphenol, total flavonoid, and electron donating ability, respectively. The electron donating ability and nitrite scavenging effect were improved with an increase of ethanol concentration, rather than the extraction temperature. ORAC (Oxygen Radical Absorbance Capacity) with extraction conditions was 1,636.47~2,696.99 ${\mu}moles$ TE/g, and was increased with the increase of extraction temperature and 40~60% of ethanol concentration. Estimated conditions for the maximized extraction including the yield, total polyphenol, electron donating ability, nitrite scavenging effect, and ORAC, were $60{\sim}68^{\circ}C$ in extraction temperature, 6~7 hr in extraction time, and 38~60% in ethanol concentration.

• Korean Journal of Remote Sensing
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• v.37 no.5_1
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• pp.1111-1124
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• 2021

Mudflats are crucial for understanding the ecological structure and biological function of coastal ecosystem because of its high primary production by microalgae. There have been many studies on measuring primary productivity of tidal flats for the estimation of organic carbon abundance, but it is relatively recent that optical remote sensing technique, particularly hyperspectral sensing, was used for it. This study investigates hyperspectral sensing of chlorophyll concentration on a tidal flat surface, which is a key variable in deriving primary productivity. The study site is a mudflat in Geunso bay, South Korea and field campaigns were conducted at ebb tide in April and June 2021. Hyperspectral reflectance of the mudflat surfaces was measured with two types of hyperspectral sensors; TriOS RAMSES (directionalsensor) and the Specim-IQ (camera sensor), and Normal Differenced Vegetation Index (NDVI) and Contiuum Removal Depth (CRD) were used to estimate Chl-a from the optical measurements. The validation performed against independent field measurements of Chl-a showed that both CRD and NDVI can retrieve surface Chl-a with R² around 0.7 for the Chl-a range of 0~150 mg/m² tested in this study.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2000.05a
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• pp.189-194
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• 2000

1) Crab shell의 납 흡착 실험결과 Langmuir 흡착 등온 모델에 잘 적용되었으며 $q_{max}$은 335.4 mg/g이었다. 2) 12시간 흡착 반응시킨 후 초기 농도에 대한 납 이온 제거효율을 고찰한 결과, 초기 납 이온 농도가 207.2 mg/l 이하에서는 97% 이상의 납 이온 제거 효율을 나타내었는데, 414.4 mg/l 이상에서는 제거효율이 60% 이하로 감소하였다. 3) 납 이온 흡착 전과 흡착 후의 crab shell을 전자현미경으로 분석한 결과 crab shell의 표면과 내부의 변화를 관찰할 수 있었다.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2000.05a
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• pp.130-131
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• 2000

알루미늄판만 있는 경우보다 구리판이 첨가되었을 때 인 제거율은 높았으나 알루미늄판만 첨가하여도 수중의 인 제거가 가능하였고, 알루미늄판 표면적이 클수록 인제거 시간이 빨랐으며, 수중 전해질농도가 높을수록 인제거 시간은 단축되었고, 알루미늄판을 재 사용하였을 때는 구리판과 전해질 농도의 영향과는 상관없이 24시간만에 제거되었으며, 또한 비폭기시에는 공식이 일어나지 않아 인이 제거피지 않고 증가됨을 알 수 있었다. 또한 인이 제거되는 과정에서 COD와 질소 제거에는 영향을 주지 않음을 알 수 있었다.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.32 no.9
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• pp.46-51
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• 2003

"환기"는 생활용품 등으로부터의 오염물질 및 불특정 물질의 농도 저감이 가능하기 때문에 Sick House 대책으로서의 중요한 대책기술이다. 본 고에서는 집합주택을 대상으로 한 중앙공조 환기방식 및 배기 중앙 환기방식의 사례를 보여주고, 시스템의 구성기술과 오염물질의 농도 저감효과에 대해서 기술한다. 또한, 대표적인 오염물질인 포름알데히드의 건자재로 부터의 발산량은 온습도, 환기량 및 건자재의 표면적 비율 등의 영향인자에 따라 변화하므로, 필요 환기량은 이들의 영향요인을 고려하여야 한다는 것을 기술한다.

• Journal of dental hygiene science
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• v.12 no.4
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• pp.320-328
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• 2012

The purpose of this study was to evaluate the tooth whitening and properties of an enamel surface after treatments with tooth bleaching agents that contained dicalcium phosphate dihydrate (DCPD) and hydrogen peroxide (HP). Thirty specimens were obtained from fifteen premolar and were randomly divided into three groups (n=10): 1, 3.5% HP + 0 g DCPD; 2, 3.5% HP + 0.1 g DCPD; 3. 3.5% HP + 1 g DCPD. All groups were bleached 8 hours per day for 14 days. With increasing DCPD concentration, the pH values in the agents increased, making it less acidic. However, there was no statistically significant difference (p>.05). As the concentration of DCPD was increased, the concentration of Ca and P was also increased. In all groups, after the tooth whitening, the tooth color was found to have a value of $L^*$ (p<.05). All groups showed significantly decreased enamel microhardness compared to their baseline (p<.05). The percentage microhardness loss (PML) of the group A1 and A2 were significantly lower than that of group A3. The obvious variation of morphology was observed on enamel surfaces in group A1. Following an analysis of the constituents of enamel surface after bleaching, as DCPD content was increased, the amount of Ca and P was increased. In this study, the experimental results suggest that DCPD/HP agent less demineralization changes such as the erosion morphology and hardness loss without compromising whitening efficiency.

• Journal of the Mineralogical Society of Korea
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• v.24 no.2
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• pp.73-82
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• 2011

X-ray absorption spectroscopy (XAS) study was conducted using arsenite-sorbed two-line ferrihydrite to investigate the mechanism of surface interactions between two-line ferrihydrite and As(III) (arsenite) which are ubiquitous in nature. The two-line ferrihydrite used was synthesized in the laboratory and the study was undertaken at pHs 4 and 10 to compare the difference in mechanisms of surface interaction between acidic and alkaline environments. The effect of arsenite-adsorbed concentrations on surface complexation was investigated at each pH condition as well. From the results of XAS analyses, the structural parameters of arsenite in the EXAFS revealed that the coordination number and distanceof As-O were 3.1~3.3 and 1.74~1.79 ${\AA}$, respectively, which indicate that the unit structure of arsenite complex formed on the surface of two-line ferrihydrite is $AsO_3$. The dominant structures of As(III)-Fe complex were examined to be bidentate binuclear comer-sharing ($^2C$) and the mixture of bidentate mononuclear edge sharing ($^2E$) and $^2C$ appeared as well. At pH 4, arsenite complex showed different structures on the surface of two-line ferrihydrite, depending on the adsorbed concentrations. At pH 10, on the contrary, the surface structures of arsenite complexes were interpreted to be almost identical, irrespective of the adsorbed concentrations of arsenite. Consequently, this microscopic XAS results support the results of macroscopic adsorption experiments in which the surface interaction between arsenite and two-line ferrihydrite is significantly influenced by pH conditions as well as arsenite concentrations.

• KSBB Journal
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• v.18 no.2
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• pp.107-110
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• 2003

Biodegradable polymers, poly(lactic-co-glycolic acid) (PLGA), poly(3-hydroxybutyrate) (PHB), and medium chain length polyhydroxyalkanoates (MCL-PHA) containing rose bengal (model drug) were coated onto the surface of stainless steel (stent materials) and their in vitro release characteristics were investigated. Drug release increased with; decreasing PLGA concentration, increasing rose bengal concentration, and Increasing dip-coating duration. The order of drug release from the polymer coating was: PHB > PLGA > MCL-PHA. These results suggest that drug release can be controlled by: changing the concentration and type of polymer, the drug concentration, and the dip-coating duration.

• Conservation Science in Museum
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• v.6
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• pp.67-71
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• 2005

We conduct the conservation treatment for the wooden well bucket excavated from civilian remains in Siji-Dong, Daegu. This bucket was in very poor condition, having been buried for a long time; thus, cetyl alcohol was used for the conservation. After replacing the water inside the wooden material with alcohol, the density of the cetyl alcohol was increased by 20, 40, 60, and 80% and immersed for two weeks at each step. After completing the immersion procedure, the remaining cetyl alcohol was removed, and the bucket, dried under normal atmosphere.